Previously, a valve drive apparatus, which drives two valves of a supercharger, has been known. For example, JP2010-281271A discloses a valve drive apparatus, which has a single actuator that drives two valves (first and second valves) of a two-stage supercharger. This valve drive apparatus includes a link mechanism placed between the actuator and the valves. A drive force of the actuator is transmitted to the valves through the link mechanism.
In the valve drive apparatus of JP2010-281271A, the second valve is urged in a closing direction thereof by a spring and is thereby held in a valve closed state until the first valve is opened to a predetermined opening degree or larger. When the first valve opens to the predetermined opening degree or larger, the second valve is opened by the link mechanism synchronously with the first valve. When the second valve is opened synchronously with the first valve, the urging force of the spring is applied to the first valve and the second valve. In the valve drive apparatus of JP2010-281271A, the link mechanism is formed with a large number of constituent members and is thereby complicated. Thus, the costs of the constituent members of the valve drive apparatus and manufacturing costs of the valve drive apparatus may be disadvantageously increased.
Furthermore, depending on an action angle of a link node of the link mechanism, a transmission efficiency of the drive force of the actuator may possibly be deteriorated. JP2010-281271A does not disclose a structure, which improves the transmission efficiency of the drive force.
When the second valve is opened, the urging force of the spring is applied to an output shaft of the actuator through the link mechanism. Therefore, in a case where the second valve is mainly opened as the operation of the internal combustion engine, the load of the actuator is increased, and thereby the stress on the actuator may possibly be increased. Furthermore, in a case where the actuator is an electric actuator, electric power consumption may possibly be increased.
Furthermore, in the range, which is from the starting of the opening of the first vale to the starting of the opening of the second valve, i.e., the range, in which the first valve can be opened without receiving the urging force of the spring, is determined by a gap between the first member and the second member. A size of the gap between the first member and the second member may vary depending on variations of the constituent members, and thereby it may be difficult to accurately set the above-described range.